Question

\(X-15\sqrt{X}+56=0\). Tìm X

 

Answer 1

\(X-7\sqrt{X}-8\sqrt{X}+56=0\)

\(\sqrt{X}\left(\sqrt{X}-7\right)-8\left(\sqrt{X}-7\right)=0\)

\(\left(\sqrt{X}-8\right)\left(\sqrt{X}-7\right)=0\)

\(\sqrt{X}=7\Leftrightarrow X=49\)

\(\sqrt{X}=8\Leftrightarrow X=64\)

Answer 2

ĐKXĐ: \(x\ge0\)

\(\Rightarrow\left(\sqrt{x}-8\right)\left(\sqrt{x}-7\right)=0\)

\(\Rightarrow\sqrt{x}-8=0\Rightarrow\sqrt{x}=8\Rightarrow x=64\)(nhận)

hoặc \(\sqrt{x}-7=0\Rightarrow\sqrt{x}=7\Rightarrow x=49\)(nhận)

Vậy x = 64; x = 49